The near instantaneous speed and extremely low cost of email communications via the internet have truly revolutionized personal and business communications. As a result, access to and use of email is becoming nearly universal. Unfortunately, the large number of email users together with the extremely low cost of transmitting emails also facilitates the mass distribution of unwanted, unsolicited emails (spam) by parties unknown to the recipients of the emails. Spam is a problem because it unproductively consumes network resources and the recipients' computer resources. Spam e-mail also places a huge burden on recipients who are forced to sort through a high volume of spam in order to separate those emails which are wanted by the recipient from the unwanted spam. Even more serious is that fact that much spam is criminal in nature, transmitted by the sender for the explicit purposes of defrauding or victimizing the recipient, and/or invading the recipient's computer and/or computer network(s). Additionally, spam e-mails may contain harmful, malicious software, and/or can obtain proprietary information from the recipient or from the recipient's computer or computer network.
It is well documented that unwanted spam comprises the majority of email traffic over the internet. Software of various kinds is available to reduce the problems and risks caused by spam. In general, such software attempts to identify spam email (filtering) and/or examine the content of emails and email attachments for harmful or malicious content (screening). While such software is effective to some degree, it is costly, requires periodic attention or maintenance, is not 100% effective in detecting spam (false negatives), can erroneously block legitimate emails (false positives), and does not reduce the volume of spam traffic nor the demand on the recipients' network and computer resources.
Not only does spam cause costly and annoying operational problems, it is difficult for the recipient of spam to access legal remedies which are theoretically available. The main reason that legal remedies are difficult to access is that the matter of the applicable legal jurisdiction is difficult to document and establish.
Further exacerbating the spam problems is that fact that the internet is ad hoc in the sense that each user is free and responsible to decide how to access and use the internet and what operational policies, procedures and software to apply and use. While the underlying technical details such as communications protocols, are established by adopted standards, there are no such standards covering operational matters such as spam filtering or screening. One unfortunate result of this situation is that there are many minimally secured or completely unsecured computers connected to the internet (sometimes known as open relays) which are easily exploited by senders of spam (spammers) to greatly multiply their ability to rapidly flood the internet with high volumes of spam.
Another consequence of the ad hoc nature of the internet is that spammers can remain anonymous. They achieve anonymity by misrepresenting their identity when they originate the spam, or by fraudulently misrepresenting the spam sender when exploiting open relays to broadcast the spam. To date, various attempts to deny spammers anonymity such as Sender Policy Framework (SPF) have not be very successful.